This project is primarily aimed at understainding factors regulating cyclic AMP metabolism in brain tissue. In addition to characterizing the receptors responsible for the augmented accumulation of cyclic AMP brought about by known neurohumoral agents (e.g., norepinephrine, adenosine, histamine), it is proposed to search for and identify unknown endogenous agents. The search for such agents is prompted by the inability to explain the effects of depolarizing stimuli (e.g., 40mM K ions) on the accumulation of cyclic AMP in brain slices in terms of the release and action of known endogenous agents, acting singly or in combination.